Exhibit 99.1

Rex Energy Exceeds High-End of Production Guidance and

Increases Full-Year 2012 Guidance

STATE COLLEGE, PA, May 1, 2012 (GLOBE NEWSWIRE) – Rex Energy Corporation (Nasdaq: REXX) today announced its first quarter 2012 operational and financial results as well as second quarter 2012 and revised full year 2012 guidance.

First Quarter Operational and Financial Results

Operating revenue from continuing operations was $33.8 million for the first quarter of 2012, which is a 46% increase over the same period of 2011. Commodity revenues, including cash settled derivatives, were $35.3 million, of which 57% was attributable to oil and natural gas liquids and 43% was attributable to natural gas. Realized prices for oil, including cash-settled derivatives, were $98.08 per barrel. Realized prices for natural gas, including cash-settled derivatives, were $3.72 per Mcf and realized prices for NGLs were $48.98 per barrel, which was 48% of the average quoted NYMEX price for the first quarter.

As adjusted, lease operating expenses (LOE) from continuing operations for the first quarter of 2012 were $9.5 million, or $1.72 per Mcfe. This amount excludes $2.8 million for the one-time retroactive portion of the new Pennsylvania impact fee, which became effective within the first quarter of 2012. The $1.72 per Mcfe is a 40% reduction in LOE on a per unit basis as compared to the first quarter of 2011. The first quarter reduction is attributable to economies of scale and operational efficiencies realized within the company’s Marcellus shale operations. In addition, the Illinois Basin experienced mild winter weather conditions and minimal spring flooding activity during the first quarter, which resulted in lower lease operating expenses. Going forward, the company will account for the Pennsylvania impact fee under lease operating expenses and will continue to exclude the one-time retroactive portion from further analysis.

As a result of the first quarter reductions in lease operating expense and continued efficiencies in the Marcellus operations, Rex Energy is lowering full-year 2012 LOE guidance to a range of $48.0 million to $53.0 million from the previously announced range of $50.0 million to $55.0 million. This revised guidance includes the current year estimated impact fee of $2.8 million and excludes the retroactive portion of $2.8 million.

Cash general and administrative expenses from continuing operations were $4.9 million, a 6% decrease over the first quarter of 2011, and fell within the company’s previously announced guidance range.

Net income from continuing operations for the first quarter 2012 was $3.8 million, or $0.08 per share. Loss from discontinued operations for the first quarter of 2012 was $5.4 million, or $0.11 per share. EBITDAX from continuing operations, a non-GAAP measure, was $21.5 million for the first quarter.

This was an increase of 86% over the first quarter of 2011. A reconciliation between EBITDAX and GAAP net income is presented in the financial highlights attached to this release.

The company incurred impairment expenses of $2.8 million from continuing operations in the first quarter of 2012 related to undeveloped acreage. The acreage is primarily located within the company’s dry gas non-operated position in Clearfield County, PA. These leases are not considered part of the company’s core position and will not affect its potential drilling locations. The acres associated with these leases will continue to be counted in the Marcellus acreage totals until they reach the end of their term.

Production Update

Rex Energy exceeded the high end of its first quarter production guidance of 60.0 MMcfe/d by approximately 1% with an average daily production rate of 60.7 MMcfe/d. This represents an increase of 23% over the fourth quarter of 2011 and 120% over the first quarter of 2011. Oil and natural gas liquids accounted for 26% of the total net production for the quarter.

First Quarter Capital Investments

During the first quarter of 2012, the company made operating capital investments of approximately $39.3 million, of which $35.3 million was used to fund the company’s Marcellus and Utica operations, $3.3 million was used to fund the company’s Illinois water flood enhancement and ASP projects, and $0.7 million was capitalized interest. The Marcellus capital investment funded the drilling of eight gross (4.4 net) wells, fracture stimulation of four gross (1.7 net) wells, placing five gross (2.4 net) wells into service and other projects related to drilling and completing wells in the Marcellus region. An additional $16.8 million was spent on leasing in the Marcellus and Utica shale operating areas. A detailed land and leasing update is given below.

Operational Update

Note: Unless specifically stated otherwise in this operational update, all numbers are gross.

Appalachian Basin – Butler Operated Area, Pennsylvania

In Butler County, Pennsylvania, the company has drilled five gross (3.5 net) wells year-to-date, with six gross (3.1 net) wells fracture stimulated and five gross (2.4 net) wells placed into sales. The company currently has 18 gross (12.6 net) wells drilled and awaiting completion with another three gross (2.1 net) wells completed and awaiting pipeline infrastructure.

The company has completed all seven wells on the Grosick pad and the wells are currently flowing into the Sarsen Plant, Rex Energy’s jointly-owned cryogenic gas processing facility, at restricted rates. Additionally, the company has completed fracture stimulating two wells on the Carson pad. These wells were drilled with 4,000’ laterals and completed using the company’s “Super Frac” design. This new design includes higher sand concentrations and a reduced cluster spacing (RCS) completion technique. This “Super Frac” design was tested by the company during its 2011 program on three other wells. The longest producing of the three wells is the Drushel #3H, which has been producing for over one year. At March 31, 2012, this well had an estimated EUR of 8.8 BCFE, and with ethane recovery this EUR would

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be approximately 11.0 BCFE. Finally, the five well Gilliland pad is currently undergoing completion operations and is expected to be completed in advance of commissioning the Bluestone Plant, the company’s second jointly-owned cryogenic gas processing facility. The connection of the Gilliland pad to sales will also include the company’s Burkett shale test well, which has been shut in since its initial test rate. For a full list of wells and well status, please see the company’s updated corporate presentation, which is available at www.rexenergy.com under the “Events and Presentations” menu of the Investor Relations tab.

In the first quarter, the company placed the Cheeseman 1H well into service. As previously announced, the well was drilled and completed in 2011 within the dry gas window of the Utica Shale and tested at an initial 24 hour rate of 9.2 MMcf/d. After being placed into service the well was curtailed for 30 days and produced at an average rate of 3.6 MMcf/d. During the past 30 days the well produced at an average test rate of 5.3 MMcf/d. The well continues to be constrained pending final completion operations. The company plans to drill one additional Utica Shale well, the Hufnagle 1H, in Butler County in 2012. Finally, the company plans to complete both its Super Rich Marcellus and Upper Devonian Rhinestreet tests during the fourth quarter.

The company’s midstream partners at Keystone Midstream operated the Sarsen Plant at an average inlet of approximately 34.3 MMcf/d during the month of March, including two days during the month in which the plant was shut down for maintenance. Additionally, Keystone Midstream commissioned the Voll Compressor Station in March of 2012, increasing capacity at the Sarsen Plant to 40.0 MMcf/d.

Keystone Midstream’s second cryogenic processing plant in Butler County, the Bluestone Plant, is on track to be commissioned at the end of May 2012. The expected inlet capacity of the Bluestone Plant is 50.0 MMcf/d.

Appalachian Basin – Warrior Prospect, Carroll County, Ohio

As previously announced, Rex Energy recently spud its first horizontal Utica Shale well, the Brace 1H, in April. The well is currently approaching vertical TD, at which time it will be logged and side-wall cores taken. The well will have a 4,500’ lateral drilled and the fracture stimulation treatment is scheduled for the middle of June. The company anticipates providing an update on the well status during the second quarter conference call in August. The company plans to drill two additional horizontal Utica Shale wells in its Warrior Prospects in 2012.

The company has closed on the previously announced 15,000 acres in the Warrior Prospect. Approximately $6.2 million was spent during the first quarter on leasing efforts in the region. The Warrior Prospect acreage cost an average of approximately $3,900 per acre. The company is continuing to pursue additional leases in the area that will be accretive to its operational development.

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Warrior South Prospect – Guernsey, Noble & Belmont Counties, Ohio

The company entered into a new Joint Development Agreement with MFC Drilling, Inc. (“MFC”) and ABARTA Oil & Gas Co., Inc. The new AMI is located in the tri-county area of Guernsey, Noble and Belmont Counties, Ohio and is being referred to as the Warrior South Prospect. The initial acreage contribution encompasses approximately 4,500 gross (2,800 net) acres and is being obtained on a “drill-to-earn” basis. The initial commitments are to drill and complete one well and commence the drilling of two others by November 15, 2012. In order to maintain its rights, the company would be required to drill and complete three additional wells each year until it has satisfied the carry obligation. The company is continuing to actively lease in the area.

Appalachian Basin – Westmoreland, Pennsylvania

In the company’s non-operated area in Westmoreland County, Pennsylvania, where WPX Energy serves as the operator, WPX completed seven wells in the fourth quarter of 2011 and currently has no additional completion operations planned for 2012. The combined average 120 day sales rate from the seven most-recently completed wells at the Marco and National Metals pads are now trending 50% above the 4.2 BCF type-curve. Two of the wells on the National Metals pad were also completed using reduced cluster spacing or RCS completion methods. These wells are on trend to exceed our recent estimates of a 6.0 BCF type curve. For the month of March, the average production rate in the Westmoreland non-operated area was approximately 62.8 MMcf/d.

Appalachian Basin – Clearfield and Centre Counties, Pennsylvania

In Clearfield and Centre Counties, the average production rate for the month of March was 10.2 MMcf/d. WPX, the company’s operator in the area, is not planning any further development in the Clearfield and Centre county areas for the remainder of the year.

Illinois Basin – ASP Project Update

In Rex Energy’s ASP project areas in the Illinois Basin, the company continues to move forward with its expansion into the 58 acre Perkins-Smith area. The company expects to begin ASP flooding of the Perkins-Smith project in the second quarter of 2012. In the high impact Delta Unit, the company has cut the cores to support the technical work and will start drilling the pattern wells in the second and third quarter of 2012. Full ASP injection is still on track to begin in the second quarter of 2013. For the first quarter, the Middagh ASP pilot averaged 60.7 gross BOPD. This compares to the previously reported range of 65.0-75.0 gross BOPD reported in the fourth quarter of 2011. The pilot continues to support the year-end proved reserves booking of 13% of pore volume recoveries.

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Appalachian Basin – Marcellus Land Update

The company increased its acreage position by approximately 3,300 gross Marcellus acres during the first quarter, of which 1,200 acres were located in the Butler Operated Area, bringing its total acreage position in this area to approximately 68,400 gross (46,000 net) acres. The company believes this additional acreage adds approximately 46 gross wells to its Marcellus and Upper Devonian potential well counts in the Butler Operated Area. The majority of the remaining 2,100 net acres are located within Westmoreland County, bringing our total acreage position in this area to 16,700 gross (9,400 net) acres. Of the total $10.6 million spent on leasing in the Marcellus areas during the first quarter, $670,000 is expected to be reimbursed in the second quarter by Sumitomo.

Midstream and Niobrara Asset Divestiture

As previously announced, Rex Energy is actively evaluating potential opportunities to divest its jointly-owned midstream assets and its Niobrara assets. The marketing process for each of these initiatives continues to progress. Based on the current status and anticipated timing of the potential transactions, the company expects to provide an update to the market on these planned asset divestitures within the next two weeks.

Second Quarter and Full Year 2012 Guidance

Rex Energy is providing the following guidance for the second quarter of 2012 and full year 2012 ($ in millions):

Conference Call Information

Management will host a live conference call and webcast on Wednesday, May 2, 2012 at 10:00 a.m. ET to review first quarter 2012 financial results and operational highlights. All financial results included in this release and discussed on the first-quarter conference call will remain subject to our independent auditor’s review. The telephone number to access the conference call is (877) 849-6312. Presentation slides containing reference materials for the call and webcast will be available on the company’s website, www.rexenergy.com, under the Investor Relations tab. The replay of the event and reference materials will be available on the company’s website through June 3, 2011.

About Rex Energy Corporation

Rex Energy is headquartered in State College, Pennsylvania and is an independent oil and gas exploration and production company operating in the Appalachian and Illinois Basins within the United States. The

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company’s strategy is to pursue its higher potential exploration drilling prospects while acquiring oil and natural gas properties complementary to its portfolio.

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Forward-Looking Statements

Except for historical information, statements made in this release, including those relating to the company’s financial guidance and projections for second quarter and full year 2012, leasing plans and expected expiries, timing and nature of Marcellus and Utica Shale development plans, planned testing of Upper Devonian Rhinestreet and “Super Rich” Marcellus prospects, expected commissioning of the Bluestone cryogenic processing plant, anticipated timing for results of the Brace 1H, drilling and completion schedules for 2012 for the company and its operating partners, anticipated fracture stimulation activities, the ASP pilot and expansion plans in the Illinois Basin, and anticipated developments and timing with respect to the potential divestitures of the company’s midstream and Niobrara assets are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Forward-looking statements typically contain words such as “expected”, “expects”, “scheduled”, “planned”, “plans”, “anticipates” and similar words and are based on assumptions and estimates that management believes are reasonable based on currently available information; however, management’s assumptions and the company’s future performance are subject to a wide range of business risks and uncertainties. There is no assurance that these goals and projections can or will be met and investors are cautioned not to rely on these forward-looking statements. A number of factors could cause actual results to differ materially from those in the forward-looking statements, including (without limitation) the following:

The company undertakes no obligation to publicly update or revise any forward-looking statements. Further information on the company’s risks and uncertainties is available in the company’s filings with the Securities and Exchange Commission.

The company’s internal estimates of reserves may be subject to revision and may be different from estimates by the company’s external reservoir engineers at year end. Although the company believes the expectations and forecasts reflected in these and other forward-looking statements are reasonable, it can give no assurance they will prove to have been correct. They can be affected by inaccurate assumptions or by known or unknown risks and uncertainties.

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For more information, please visit our website or contact:

www.rexenergy.com

Tom Stabley

Chief Executive Officer and Chief Financial Officer

(814) 278-7215

tstabley@rexenergycorp.com

Mark Aydin

Manager, Investor Relations

(814) 278-7249

maydin@rexenergy.com

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REX ENERGY CORPORATION

CONSOLIDATED BALANCE SHEETS

($ in Thousands)

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REX ENERGY CORPORATION

CONSOLIDATED STATEMENTS OF OPERATIONS

(Unaudited, in Thousands, Except per Share Data)

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REX ENERGY CORPORATION

CONSOLIDATED OPERATIONS HIGHLIGHTS

(Unaudited)

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REX ENERGY CORPORATION

OIL AND GAS DERIVATIVES – CURRENT HEDGING POSITIONS⁽¹⁾

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The following table has been added to provide clarification on the components of Gain on Derivatives, net under Other Income (Expense) on the Consolidated Statements of Operations for each of the periods presented (in thousands):

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Non-GAAP Financial Measures

EBITDAX

“EBITDAX” means, for any defined period, the sum of net income for the period plus the following expenses, charges or income, in each case, to the extent deducted from or added to net income in the period: interest, income taxes, depreciation, depletion, amortization, accretion, unrealized losses from financial derivatives, exploration expenses, and other similar non-cash charges, minus all non-cash income (without limitation) income from unrealized financial derivatives, added to net income. EBITDAX is used as a financial measure by Rex Energy’s management team and by other users of its financial statements, such as the company’s commercial bank lenders, to analyze such things as:

EBITDAX is not a calculation based on GAAP financial measures and should not be considered as an alternative to net income (loss) in measuring the company’s performance, nor used as an exclusive measure of cash flow, because it does not consider the impact of working capital growth, capital expenditures, debt principal reductions, and other sources and uses of cash, which are disclosed in the company’s statements of cash flows.

Rex Energy has reported EBITDAX because it is a financial measure used by its existing commercial lenders, and because this measure is commonly reported and widely used by investors as an indicator of a company’s operating performance and ability to incur and service debt. You should carefully consider the specific items included in the company’s computations of EBITDAX. While Rex Energy has disclosed its EBITDAX to permit a more complete comparative analysis of its operating performance and debt servicing ability relative to other companies, you are cautioned that EBITDAX as reported by the company may not be comparable in all instances to EBITDAX as reported by other companies. EBITDAX amounts may not by fully available for management’s discretionary use, due to requirements to conserve funds for capital expenditures, debt service and other commitments.

Rex Energy believes that EBITDAX assists its lenders and investors in comparing a company’s performance on a consistent basis without regard to certain expenses, which can vary significantly depending upon accounting methods. Because the company may borrow money to finance its operations, interest expense is a necessary element of its costs and ability to generate cash available for distribution. Because Rex Energy uses capital assets, depreciation and amortization are also necessary elements of its costs. Additionally, the company is required to pay federal and state taxes, which are necessary elements of its costs. Therefore, any measures that exclude these elements have material limitations.

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To compensate for these limitations, Rex Energy believes it is important to consider both net income (loss) determined under GAAP and EBITDAX to evaluate its performance.

The following table presents a reconciliation of the company’s net income (loss) from continuing operations to its EBITDAX from continuing operations for each of the periods presented

($ in thousands):

Earnings Comparable with Analyst Estimates

“Earnings Comparable with Analyst Estimates” means, for any period, the sum of net income for the period plus the following expenses, charges or income, in each case, to the extent deducted from or added to net income in the period: unrealized losses from financial derivatives, non-cash compensation expense, dry hole expenses and impairment, minus all gains from unrealized financial derivatives and deferred income tax benefits, added to net income. Earnings Comparable with Analyst Estimates is used as a financial measure by Rex Energy’s management team and by other users of its financial statements, to analyze its financial performance without regard to non-cash deferred taxes and non-cash unrealized losses or gains from oil and gas derivatives. Earnings Comparable with Analyst Estimates is not a

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calculation based on GAAP financial measures and should not be considered as an alternative to net income (loss) in measuring the company’s performance.

Rex Energy has reported Earnings Comparable with Analyst Estimates because it believes that this measure is commonly reported and widely used by investors as an indicator of a company’s operating performance. You should carefully consider the specific items included in the company’s computation of this measure. You are cautioned that Earnings Comparable with Analyst Estimates as reported by Rex Energy may not be comparable in all instances to that reported by other companies.

To compensate for these limitations, the company believes it is important to consider both net income determined under GAAP and Earnings Comparable with Analyst Estimates.

The following table presents a reconciliation of Rex Energy’s net income (loss) from continuing operations to its Earnings Comparable with Analyst Estimates for each of the periods presented ($ in thousands):

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